So I purchased this 1995 E420 2 days ago after a good 20 minute test drive on the interstates and downtown Atlanta traffic. During the test drive the coolant like would blink on but never stay on constantly. Temperature gauge stayed at 80 with downtown traffic and on the interstate. Drove home with no problems and checked coolant reservoir once car cooled down and added a little 50/50 mixture.

Yesterday, went to change over title and tag and drove the car in traffic for about 40 minutes and gauge stayed at 80. Went to pick daughter up from school and had to wait. After she gets in the car I noticed that the temp gauge is near 100 but slowly lowers back to about 90. When I get home I let car idle to see how far gauge will rise and it rises up to the 100 mark. I shut the car off at this point. Had to run errands and did not get back in time to run any further test.

This morning I drive to work, 60 miles and halfway thru trip hit traffic. Temp reading had been 80 the entire trip with the heat on for warmth. In traffic I see the gauge start to rise and hit the 100 mark then it continues to rise to almost half distance between 100 and 120. At this point I turn the heater back on and temp stabilizes. It was only after the traffic started to move that the temp came back down to 80. When I got to work I set in the car again to let idle and temp rose to slightly over 100, got out of the car and listen for the fans. No fans were on at this point. I have read most of the overheating threads and know that I need to check the temp sensor and also the clutch fan. What is the newspaper test and is there anything else to look for at this point. Car was kept up and is very clean. No leaks or anything so I don't think this is a lemon.

 

do the fans come on ever? like if you turn on the ac, do they ever come on or always off?
It sounds like the temp rises very quickly, maybe the coolant is not circulating properly? try squeezing the upper hose to see if there is an air lock and force the air through?
If the radiator is original, does it have a lot of debris and dirt in it that might be affecting how it cools?
Maybe fan clutch/thermostat is bad?

 

Funny you ask about the fans and AC. At lunch today I turn on the auto climate to cold and the fan did not come on at all. What is stranger is that I let the car idle for about 5 minutes and then gave it gas for more engine heat, but the gauge moved really slowly to the 100 mark but barely. I think I will check the fan clutch when I get home. Also, how do you check the fans and fan clutch? Want to make sure I am doing this correctly.
As far as radiator hose I will feel and check. Its weird that you mention the Thermostat because every car that I have ever owned the thermostat always stopped working in the open position. Even in the Saab 9-3, each time the T-Stat went out it was open.

 

IIRC, the aux fans should come on @107°C. My '93 400E ran like yours, 80°-90°C all the time but on warm days and in traffic would creep toward 100°C, especially running A/C in traffic. It developed a radiator leak where the pipe joined the tank. When I replaced the radiator I noticed that the old one, although quite empty, weighed more than twice what the new one did. Popped a tank off, and it had just a minor bit of sediment and some light deposits which seemed pretty evenly distributed. Nothing horrible, but certainly had an effect. New radiator and new coolant and she never went over 80°C until sitting in traffic in the hottest days of summer(95°F+) with the A/C on. Only other issue was the 30A strip fuse for the aux fans which failed the last summer I had the car. This allowed the temp to go up to about 110°C one day in bumper to bumper traffic with 100°F+ ambient temp. Check your fans, check your radiator, check your coolant condition.

 

Thanks for the info. I am pretty sure the fans never came on even with the AC running. I have my physical today and will check then.

 

Yesterday, after coming home from the doctors office I let the car go up to over 100 and checked the fans. Neither one was running. I also just happen to have a newspaper and tried to stop the fan twice and it kept running, so I am going to check the fuses next. It would seem ironic that both fans stopped running. Fuse seems to be a good start. Will let you all know.